Silo Failure

7/30/2019 Silo Failure

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ThisreportiscopyrighttoRHIwrittenanduploadwithsomemodificationtohidetheclientnameforeducationalproposeforanycommentspleaseemailkhaled_eid@yahoo.com

ReviewReport

ClientCementCompanyUnburnedclinkersteelsilo

11/18/2011

11/18/2011 Eng.AmedSaeedCivilEng.Khaled

Eid,Msc,PE

Civil

0Date Writtenby Reviewedby Approvedby Version


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Contents1 Introduction.......................................................................................................................................... 3

2 Unburnedclinkersilo............................................................................................................................ 3

2.1 Receiveddocumentsanddrawings.............................................................................................. 4

2.2

Reviewmethodology

....................................................................................................................

5

3 Analysisinputdata................................................................................................................................ 5

3.1 FiniteElementProgram................................................................................................................ 5

3.2 Temperatureeffect....................................................................................................................... 6

3.3 Windload...................................................................................................................................... 6

4 Design.................................................................................................................................................... 6

4.1.1 Silowall................................................................................................................................. 6

4.1.2 Silobottomhopper............................................................................................................... 7

4.1.3 Siloroof................................................................................................................................. 7

4.1.4 Silosupportingconcretestructure....................................................................................... 7

5 Fabricationanderection....................................................................................................................... 8

6 Summaryandconclusion...................................................................................................................... 9

7 Recommendation.................................................................................................................................. 9

References.................................................................................................................................................. 10

Appendix1................................................................................................................................................. 11

Appendix2

.................................................................................................................................................

12

Appendix3................................................................................................................................................. 13


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1IntroductionClientCement(CLIENT)plant islocatedinClient,Elkarak

Jordon90KmsouthAmman.Thedryprocessplanthasa

productionof5000tonperdaystartedcommissioningin

September2010.

MechanicallydesignedbyXXX,Germanyreferred

inthisreportasthemechanicaldesigner.

Managedbythe consultantHOLTEC,India

referredinthisreportastheconsultant.

CivildesignengineerTEM,Turkeyreferredinthis

reportasthedesignerorcivildesigner.

ThecontractoristheMIDCONTRACTING,

AMMANreferredinthisreportasthe

contractor.

At the requestofClientcement fromRHI to review the

structural design and construction integrity for the

unburnedclinkersilo

RHIvisitedthesiteon29thofNovember2011andtalked

to concerned parties then inspected the silo, it was

noticedthesiloisemptyandmaterialisaccumulatedon

the concrete platform below as a sign of emergency

discharge.Stairaccesswascoveredwithmaterialinsuch

it is during initial filling operation the silo bottom deformed as shown and there are is sign of

deformationatthesupportingringbeamalsothereisacrushinginthebearingareaatthesilosupport

Refertoappendix1forphotos.

2 UnburnedclinkersiloTheunderburnetsiloisdesignedtostoretherejectedclinkersoitmayberecycled bysomeratiointhe

processagain.Usuallystoredinsiloseithersteelorconcrete.Inourcaseitisasteelsilowithadesigned

capacityof1500tonbasedonclinkerdensityof1.3ton/m3,thesilodiameteris10meterandheightof

16.0meterwithaflat bottomhopperbottomdiameterof7.5meterandheightof3.75meter.Thesilo

issupportedatlevel15.2onfourconcretebeamssupportedinfour concretecolumns.


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2.1 ReceiveddocumentsanddrawingsThesedrawingweresubmittedbyClientCementCompanyasthelatestgeneralarrangementdrawings.

FabricationdetailsofunderburnerXXX 84189756BAsheet1

FabricationdetailsofunderburnerXXX 84189756BAsheet2

Clinkertransportandstoragegernalarrangement 84127249UA

KCP15C001_05.dwg (15UNBURNTCLINKERHOPPER) FOUNDATIONPLAN

KCP15

C002_01.dwg

(15

UNBURNT

CLINKER

HOPPER)

+2.500

LEVEL

FORMWORK

PLAN

KCP15C003_01.dwg (15UNBURNTCLINKERHOPPER) +5.900LEVELFORMWORKPLAN



KCP15C006_01.dwg (15UNBURNTCLINKERHOPPER) COLUMNAPPLICATIONPLAN C1C2C3

KCP15C007_00.dwg (15UNBURNTCLINKERHOPPER) +2.500LEVELSLABREINFORCEMENT

PLAN


PLAN


PLAN


PLAN

KCP15C011_00.dwg (15UNBURNTCLINKERHOPPER) REBARDETAILSOFFOUNDATIONS

KCP15C011_01.dwg (15UNBURNTCLINKERHOPPER) REBARDETAILSOFFOUNDATIONS

KCP15C012_00.dwg (15UNBURNTCLINKERHOPPER) BEAMDETAILS B001B002B003B004

B005B006B101B102B103B104

B105B106B107B108B109B110B204

KCP15C013_03.dwg (15UNBURNTCLINKERHOPPER) BEAMDETAILS B111B201B202B203

B205B206B207B208B209B210

B211B212B213B214B215B216B301


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KCP15C014_02.dwg (15UNBURNTCLINKERHOPPER) STAIRPLANANDDETAILS

2.2 ReviewmethodologyDespiteof RHIrequestedseveraltimesfromCLIENTtoprovide

theoriginaldesigncalculationbutwedidnotgetanythingtill

nowwhichraiseaquestionifthisstructurewasalready

designedbyXXXornot?Andhowitwasapprovedifthereisno

supportingdesign

document?

Thusreviewmethodologywasappliedbymakingan

independentsetofcheckanalysisandcalculations,accordingto

materialandplatethicknessprovidedinthedrawings.

Thefollowingarethecodesandstandardsusedinreview

BSEN19914:2006ActionsonstructuresSilosand

tanks.

LoadscombinationstotheASCE705 minimumdesign

loadsof

structure

Wind,snowandthermalloadsareaccordingtothe

Jordanianloadingcode.

DesignofsteelmembersaspertheAmericancode

AISCASD.

MechanicalloadsappliedexactlyasprovidedbyXXX

onlywindloadsarecalculated.

3 Analysisinputdata3.1 FiniteElementProgramThereisnoprogramyettopredictthematerialflowsointhisstudythesilobucklingbehaviorwas

investigatedwithlinearbucklinganalysisofSAP2000(Nonlinearv.14).SAP2000isageneralpurpose

structuralfiniteelementanalysisprogram.Allcircumferentialandlongitudinalstiffenersweremodeled

asframeelements.


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3.2 TemperatureeffectTheouterwallsofthesilocanexpandduringdayandcontractatnightasthetemperaturedrops,if

thereisnodischargetakingplaceandmaterialinsidethesiloisfreeflowing,itwillsettleasthesilo

expandsbecauseitcannotpushedbackupwhenthesilowallcontract.

Atemperaturedifferenceof100degreeisconsideredduetotheaverageeffectofhotclinkerwhen

enteringthesilo.

3.3 WindloadCircularbins,ontheotherhand,areverysensitivetowindloadingbecauseofthevarying

pressure/suctiondistributionofthewindloadingaroundthecircumference,andthelackofstiffnessof

theshell

in

resisting

this

loading.

The

required

thickness

of

plate

in

the

upper

strakes

of

acircular

bin

is

oftendeterminedbythewindloading.

Windbucklingischaracterizedbythe

formationofoneormorebuckleson

thewindwardfaceoftheshell.Wind

alsoproducesanoverturning

momentonatallbin,whichinducesa

verticalcompressivestressinthe

leewardface;thisreacheda

maximumatthebaseofthebin,

wheretheshellneedstobechecked

againstbuckling

4 DesignAsstatedbeforenoinformation

abouthowthissiloisdesignedto

whichcode,didanychangedineither

heightorbottomduringerection?no

historicalinformationavailable.

Sothisreportwillnotbeabletojudgethedesigncalculationbutwillonlyrefertotheasbuiltonsite

andXXX

drawing

841

89

756BA

rev

2.

4.1.1 Si lowallSilomaterialdoesnotactlikeafluid;drymaterialshavefrictionalorcohesiveresistanceandtendto

formdomeswiththesilowallthatpreventsitfromfallingfreelydownward.

Thelateralpressureonthesiloshellfromthedrymaterialsisofdifferentcharacterthanthelateral

pressureontheretainingwallfromsoilatthebackofthewall.


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Thedesignerappliesaconstant10mmthicknessfor

thewallandthebottomhopper;practicallyitistoo

smallwhenconsideringallowanceforrustand

aberrationforsuchlargesizesilos.Thecritical

bucklingstressinthewallisgoverningthethickness

requiredtocarrytheverticalcompressionload.

Itwasfoundbyanalysisthatthesilowallisonlysafe

atthetopthirdofthesilobutinallotherlocationis

unsafestressandbuckling.

4.1.2 Si lobottom hopperThebottomhopperisdesignedas 10mmwithadiameterof7.5meterstiffenedbyangle75x10,itis

foundtobeawayunsafeaswell.Refertoappendix3fordetails.4.1.3 Si loroofThetoproofwithplate10mmisfoundtobesufficienttosupporttheappliedliveloadsbutthe

supportingsteel beamsareunsafe(thebeamspansforsevenmetersandsupportingawidthofoneand

halfmeterandassignedasUPN200).

4.1.4 Si losupport ingconcrete st ructure

Thesiloissupportedinfourbearingpointsona

200cmx90cmconcretebeamsbyvisualinspection

thesebeamssufferingfromdiagonalcracksand

concretecrushing atoneofthebearingpoints,

furthermoreconcretebeamsatlevel8.4suffering

verticalcracksinbothsides.

Itisalsovisuallynoticedinsomelocationsome

concretehoneycombscreatingavoidsinthe

concretebeams

and

left

without

curing

that

is

also

raiseaquestionabouttheconcretequality.

RHIrequestedtheconcretestructuredrawingsandrunandindependedcheckingfor the whole

structure.

IT wasfoundthatthesupportingbeamstobeunsafeinshearwithevidenceoftheshearcrack,while

forlevel8.4allbeamsaresafeaccordingtothedesignsothecracksmaybeasareasonofthefalling

materialontheapronfeederwhenthesilobottomdeforms.

Refertoappendix2forsupportingstructurechecking.


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5 FabricationanderectionAlthoughappropriatesizesasperthedesigndrawingareusedbutmanyfabricationanderectionerrors

arespottedduringinspectiongivingabadimpressionaboutthequalitycontrol.

1. Thebottomstiffenersaretackweldedandnotinfullcontactwiththesilobody.

2. Thestiffenersarenotcontinueswithagapatmidspanwhereabeigestload.

3. Thebottomstiffenersarenotconnectedtotheverticalonesthustheyarenottransferringthe

loadtothesupports.


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6 Summaryandconclusion

Ourstudyconcludesthatthe

steelsiloisunderdesigned

sufferingmanydesignissues

Theseissuesaresummarized

asfollows

Thesupporting

concretebeamisjust

safeinbendingbut

unsafeinshearby18%thisexplainsthe45degreescracks.

Duetothebottomexcessivedeformationitdamagedtheapronfeederwithamaterialfalls

addingunexpectedloadedontheconcretebeamsatlevel8.4creatingcracksinthesebeams.

Thepartymostresponsibleforthebottomcollapsewasthedesignerbecauseallitemsare

unsafethewalls,theflatbottom,thestiffening,theringbeamandtheroof,notasingleitemin

thissiloisfoundtobesafe.

The

erector

and

fabricator

work

was

away

from

standard

leading

to

decrease

more

the

capacity

howeverthiswillnotaloneleadtothecollapse

Thereisnosignforanyexcessiveusage,lackofmaintenanceoroperationalmisuse.

7 RecommendationWeproposethefollowingactionsaspartoftherectification

Wetriedmanyrepairalternativebutnoneofthemsolveallissuessowerecommend

replacingthesiloasthebestoption.

Itisadvisabletosupportthesilooneightpointstodistributetheconcentratedloadby

addingsteel

beams

at

45degree.

Thesupportingbeamswillneedtobestrengthenedagainstshear.

Crackedbeamsinlevel8.4shouldbestrengthened.

Concretebuildingshouldbeinspectedforanyconstructiondeficienciesandrepairedbefore

fillingthesilo.

Concretecoretestmayberequiredtoevaluatetheconstructedconcretequalityandif

possibletochecktheexistingsteelbarsandstirrupsatrandomlocation.

No access to the silo support to allow for inspection at bearings it is recommended to addladder from level 8.4 to 15.2


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References

1. AmericanWeldingSociety(AWS),550NW42dAvenue,Miami,FL22126.

2. RubinM.Zallen,P.E.,Collapseofsteelsilo3. AmericanIronandSteelInstitute(AISI),110117thSt.,NW,Suite1300,Washington,

4. BahaaMachaly.,Structuralsystemsforwindandearthquakeloads.5. TheJordanianloadingcodeArabic originalcopyAmman2006.6. ACIstandards31391,Standardpracticefordesingandconstructionofconcretesilosand

stackingforstoringgranularmaterials


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Appendix1Site

Photos


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Appendix2Concretebuildingreview

Notincludedinthiseducationalcopy


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Appendix3Analysisanddesignchecking forsilo

Notincludedinthiseducationcopy

Silo Failure

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